We present a system for collaborative conceptual design that allows users potentially located in geographically distant areas to cooperate by sketching, exploring and modifying their ideas interactively, with immediate visual feedback. The system supports several modeling primitives and can be easily extended with user-defined objects. In this context, we introduce the notions of animated and sketchy billboards. Applications of this system include early stages of urban and landscape design, rapid prototype of virtual environments, animation, education and recreational use.